<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
 <head>
  <title>Content Inserted in Pagination after ::before</title>

  <style type="text/css">
    body {
      font-size: 16px;
    }

    #colset {
      height: 200px;
      width: 450px;
      -moz-column-width: 150px;
      -moz-column-gap: 0;
      -moz-column-fill: auto;
      border: 3px solid silver;
    }

    #x {
      height: 500px;
    }

    #x:before {
      display: block;
      height: 201px;
      content: "";
      border-bottom: 4px solid blue;
    }

    #shift {
      height: 220px;
      border-top: 4px solid blue;
    }
</style>
</head>

<body onload="document.getElementById('x').insertBefore(document.createTextNode('This must be in the second column between two 4px blue lines.'), document.getElementById('shift'))">

<div id="colset">
  <div id="x"><div id="shift"></div></div>
</div>

</body>

</html>
